A continuing study of the causes for the interindividual variation in pharmacokinetics of propranolol in dogs and humans involving use of unique assays of the drug, its stereospecific forms, and metabolites and conjugates. The studies in dogs involve use of special dog models which allow separate study of the gut and liver metabolism and the factors which affect the rate and extent of metabolism. Also a special chronic renal impaired model is used. Studies in normal subjects and patients with liver and renal diseases are going on parallel to the dog studies.